Known mixers, as shown by German Patent Specification No. 572715, have two shafts with the drive being centrally positioned in a back gear in which distribution then takes place on to the oppositely driven mixing shafts. The mixing trough can be rotated about a longitudinal axis, which is aligned with the longitudinal axis of the main drive shaft leading into the back gear. The mixing trough is held in its normal operating position by a brake. If the brake is released, the mixing container is pivoted about its longitudinal axis and out of the normal position by friction between the mixing and kneading blades and the inner wall of the mixing trough. In order to pivot the mixing trough from the discharge position into its normal operating position, an additional friction gear is provided. This known construction is very complicated and does not readily permit control of the pivoting speed. Also, operation when the mixing trough is out of its normal position is not possible.
It is also known from German Patent Specification No. 976415 to provide a batchwise operable mixer with a mixing trough, which can be pivoted for emptying purposes. The pivoting is effected by means of a piston-cylinder drive arranged eccentrically to the pivot axis and subject to the action of a pressure medium. Thus a separate drive is provided, which is considered to be disadvantageous. It is also difficult with such drives to achieve large pivoting angles.